Electromagnetic motor switch



Oct. 20, 1942.

J. WHITE ELECTROMAGNETIC MOTOR SWITCH Filed Oct. 28, 1940 III INVEN ORATTORNEY/V Fitented Oct. 20, 1942 ELECTROMAGNETIC MOTOR SWITCH JoeWhite, Anderson, Ind., assignor to General Motors Corporation, Detroit,Micln, a corporation oi. Delaware Application October 28, 1940, SerialNo. 363,180

3Claims.

This invention relates to electromagnetic motors, for example, theelectromagnetic motor used for vibrating the diaphragm of an electrichorn. In an electric horn, the movable armature of the electromagneticmotor is mounted upon the horn diaphragm and is attracted toward thepoles of the electromagnet when the magnet is energized. During themovement of the armature toward the magnet poles, a circuit breaker isopened to disconnect the magnet coil from a current source. As fluxdecays in the magnet core, the armature continues to move toward themagnet poles until diaphragm stressbalances flux pull. Thenthe storedenergy in the diaphragm causes it to bend away from the magnet poles andto pass through neutral or nonstressed position and then to bend in adirection away from the magnet poles. As the diaphragm moves away fromthe magnet poles, the circuit breaker closes to reconnect the magnetcoil with the current source. During motion of the diaphragm away fromthe core, flux in the core is increasing from residual to a valuesuflicient to cause the diaphragm to move toward the core again and thecycle is repeated as long as the terminals of the horn are in circuitwith the current source.

In the normal at rest position of the diaphragm, the circuit breakercontacts are closed. A resilient blade carrying one of the contacts isinsulatingly spaced from a metal part carried by the armature ordiaphragm. It is therefore apparent that the operationof the horn isdependent upon the normal spacing between the metal part carried by thediaphragm and insulating member separating the metal part from thecontact carrying blade. The current consumption of the horn will begreater when said normal spacing is large, and less when said normalspacing is small. The circuit breaker may be adjusted relative to themetal part carried by the diaphragm so as to give the desired normalspacing; but, as the contacts of the circuit breaker wear away thisnormal spacing will decrease and the volume of the sound of the hornwill decrease.

It is an object of the present invention to provide for automaticallycompensating for the wear of the contacts in such manner that the normalspacing between the circuit breaker and the diaphragm actuated willremain substantially unaltered. In the disclosed embodiment of thepresent invention, this object is accomplished by providing for relativewear between the metal part carried by the diaphragm and a nonconductingpart of the circuit breaker, which transmits motion from said metal partto the spring blade carrying the movable contact of the circuit breaker.

Further objects and advantages of the present invention will be apparentfrom the following description, reference being had to the accompanyingdrawing wherein a preferred embodiment of the present invention isclearly shown.

In the drawing:

Fig. 1 is a plan view of an electromagnetic motor constructed inaccordance with the present invention.

Fig. 2 is a sectional view on the line 22 of Fig. 1.

Fig. 3 is a sectional view on the line 3-3 of Fig. 1.

Fig. 4 is an enlarged fragmentary view .of parts of the circuit breakerand the metal part carried by the diaphragm for actuating the movablecontact of the circuit breaker.

The main frame member 20 of an electric horn is secured by screws 2 Iand nuts 22 to a diaphragm, 23, a gasket 24 and a collar 25 carrying aprojector 25. Diaphragm 24 carries armature plates 21 and 28 secured byrivets one of which is the shank 29 of a stud 30 having a slightlyrounded point 3|. A central hole through the diaphragm and plates isthreaded to receive a screw 32 cooperating with a nut 33 for securing aflat bell or tone disc 34 which is caused to vibrate with a clearringing sound when the screw 32 strikes a core 35 of an electromagnethaving a coil 36 surrounding the core. The shank 31 of core 35 providesa rivet for securing to the frame 20, a reenforcing washer 38 and amagnetizable yoke 39 having parallel branches 40 providing pole pieces4| facing the armature plates 28, 21.

One end of coil 36 is connected with terminal 42. Terminal 43 isconnected with plate 44 of circuit breaker assembly 45 which includes aflexible strip 46 secured at its ends by rivets 41 to shoulders 48provided by frame 20. Rivets 49 attached to the strip 46, insulation50,contact bracket 5i, insulation 52, contact flexible blade 53,conducting plate 44, and insulation 54. Bracket 5| carries contact 55normally engaged by contact 56 carried by blade 53 and extending througha. hole in insulation 52.

Plate 44 (electrically connected with terminal 43) is in electricalcontact with blade 43. Bracket 5| is connected with magnet coil 36. Whenterminals 42 and 43 are connected with a current source (by a suitableswitch called a horn button), coil 36 is energized and armature 28, 21moves toward the core 35 to flex the diaphragm 23 in one direction andto cause' stud 30 to engage insulation 52 and to move blade 53 away frombracket to separate contact 55 from contact 55, thereby interrupting thecircuit of coil 36. The flux in core 35 decays and, finally, thediaphram 23 moves away from core 35 and flexes in the oppositedirection. During this movement, the contacts 55, 55 reclose, and thecycle of oscillations of the diaphragm is repeated as long as the hornbutton is closed.

Normally, when the diaphragm 23 is at rest, the contacts 55, 56 areclosed and there is a space between the end 3! of stud 30 and theinsulation 52. The amount of clearance which is required for the properoperation of the horn is regulated by a screw 60 threaded through theframe 20 and abutting an adjusting bracket 5! which is a part of circuitbreaker assembly 45. Strip 46 is torsionally biased to urge the bracketBl downward a distance greater than required for correct normal space ofparts 30 and 52. By threading the screw 60 upwardly (Fig. 2) the bracket6| is engaged and the circuit breaker assembly is rotated clockwise todecrease the distance between the parts 30 and 52. By threading thescrew 60 downwardly (Fig.- 2) this distance is increased. When thecorrect normal spacing of parts 30 and 52 is obtained, screw 50 islocked in adjusted position by nut 52.

Although the spacing between parts 30 and 52 may be correct at theoutset, this spacing would decrease as the contacts 55 and 56 wear down.To compensate for contact wear, the parts 30 and 52 are so constructedand arranged that relative wear between them takes place at a ratecommensurate with the rate of wear of the contacts 55 and 56. One way ofproviding for this compensating wear between parts 30 and 52 is to makepart 52 of a relatively soft substance and provide part 30 with a pointwhich will gradually form a depression 52a in part 52. In this way thenormal spacing between parts 30 and 52 remains substantially the samewhile the contacts 55 and 55 wear away. Contacts 55 and 56 are providedinitially with spherical contact surfaces. The rate of contact surfacewear is greater at the start than later. Similarly, the wear betweenparts 30 and 52 takes place more rapidly at the beginning than later.

Satisfactory compensation for contact wear has been effected, when thepart 52 is made of bakelized linen about 0.35 inch thick and the point3! of the steel stud 30 has a radius of .025 to .032 inch. Both thepoint 3! and insulation 52 wear away, but the wear of the insulation isthe greater.

While the embodiment of the present invention as herein disclosed,constitutes a preferred form, it is to be understood that other formsmight be adopted, all coming within the scope of the claims whichfollow.

What is claimed is as follows:

1. A circuit breaker comprising contacts one of which is movablerelative to the other, an actuating member mounted for reciprocato'rymovement, means for moving the actuating member, a member operativelyconnected with the movable contact and engaged by the actuating member,one of said members being pointed and the member being made of suchmaterial that a depression is worn therein due to the repeatedengagement of said members in order that the wear between said memberstends to compensate for the wear of the contacts.

2. A circuit breaker according to claim 1 in

